Schedule IV - Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Life insurance in force
Gross amount, Life insurance in force	$ 1,105,323	$ 1,047,002	$ 1,047,982
Ceded to other companies, Life insurance in force	49,172	55,399	72,208
Assumed from other companies, Life insurance in force	2,478	2,827	3,273
Net amount, Life Insurance In Force	$ 1,058,629	$ 994,430	$ 979,047
Percentage of amount assumed to net, Life insurance in force	0.20%	0.30%	0.30%
Premiums:
Gross amount, premiums	$ 32,402	$ 30,755	$ 29,812
Ceded to other companies, premiums	424	513	570
Assumed from other companies, premiums	329	384	400
Net amount	$ 32,307	$ 30,626	$ 29,642
Percentage of amount assumed to net, premiums	1.00%	1.30%	1.30%
Life insurance and annuities [Member]
Premiums:
Gross amount, premiums	$ 2,307	$ 2,881	$ 2,886
Ceded to other companies, premiums	233	310	335
Assumed from other companies, premiums	22	22	106
Net amount	$ 2,096	$ 2,593	$ 2,657
Percentage of amount assumed to net, premiums	1.00%	0.80%	4.00%
Accident and health insurance [Member]
Premiums:
Gross amount, premiums	$ 30,095	$ 27,874	$ 26,926
Ceded to other companies, premiums	191	203	235
Assumed from other companies, premiums	307	362	294
Net amount	$ 30,211	$ 28,033	$ 26,985
Percentage of amount assumed to net, premiums	1.00%	1.30%	1.10%